A brake system of this type is described in the published European patent No. 089081.
In one mode of emergency braking, when said brake system is being used, the hydraulic fluid received by the actuator in order to disengage the brake is suddenly emptied from the actuator in order to engage the brake. As a consequence therefore the vehicle may be abruptly braked, which may not be desired or even necessary under the circumstances. It is possible to control brake effect by means of a suitable microcomputer provided that electrical energy is available for such control, but in many cases the emergency braking is effected due to a shutdown of the electric power, the possibility of automatically controlling the brake effect thus being eliminated.